Impact of cigarette smoking on the outcomes of ST-elevation myocardial infarction after primary percutaneous coronary intervention in metropolitan Tehran

Objective: Although the adverse effects of smoking are well-established, evidence shows a longer survival rate following an acute myocardial infarction (MI) among smokers or the so-called “smoker's paradox”. This study aimed to determine the impact of smoking on the one-year clinical outcomes of ST-elevation myocardial infarction (STEMI) after primary percutaneous coronary intervention (PPCI) in a large registry of the Iranian population. Methods: A total of 3087 patients diagnosed with acute STEMI who underwent PPCI between 2013 and 2018 were enrolled in the study. Patients' smoking status was determined based on self-reported history and categorized into two groups: current smokers and non-smokers. Clinical and angiographic data were collected from the Tehran Heart Center (THC) registry. The primary outcome was one-year of major adverse cardiac and cerebrovascular events (MACCE). The effect of smoking on MACCE was evaluated using a Cox model. Results: From the study population, 1967 (63.7%) were non-smokers, and 1120 (36.3%) were current smokers. Non-smokers had higher rates of prior CABG (5.3%) as well as a higher history of co-morbidities, including a history of diabetes mellitus (46.0%), hypertension (52.7%) and hyperlipidemia (55.4%) than smokers (2.3%, 30.4%, 35.7%, and 49.8% respectively). Smokers had a higher reference vessel diameter than non-smokers (P=0.005). The unadjusted hazard ratios (HRs) for MACCE within one year were significantly lower in smokers than non-smokers (0.73, 95% CI: 0.58,0.92; P=0.009); however, after adjustment for confounders, the HRs for MACCE in smokers were similar to non-smokers (HR: 1.00, 95% CI: 0.73,1.38). Conclusion: The study found that smoking had no significant impact on the one-year clinical outcomes of STEMI patients after PPCI in the Iranian population. This study is the first of its kind to assess the effect of smoking on STEMI patients in Iran and highlights the need for further research in this area.